How did dinosaurs have sex?

October 6, 2000

Dear Cecil:

Hi, i have been wondering for the longest time how dinosaurs had sex?!?! Ive asked just about everybody, but i havent gotten an answer. They seam too large to have sex like humans, and their tails would get in the way for doggy-style … PLEASE ANSWER MY QUESTION!!!!!!!

— Lianna

Cecil replies:

Sure thing, Lianna. Just promise me you'll get those meds adjusted. A 1999 book squarely addresses your question: Kenneth Carpenter's Eggs, Nests, and Baby Dinosaurs: A Look at Dinosaur Reproduction. Ken, whose love of dinosaurs was sparked by seeing Godzilla when he was five, appeals to both scholarly and general readers in his book, which was published by Indiana University Press. On the one hand, we find all the academic trappings — charts, drawings, a learned bibliography. On the other hand, chapter five is entitled "How Dinosaurs Did It." Just what you'd expect from a guy who was a contributor to The Official Godzilla Compendium. No lie.

Still, you can have too much of a good thing. Early in the cited chapter we read, "The gonads … of both birds and reptiles are confined within the body so it is safe to assume the same was true of dinosaurs. With nothing hangin' in the breeze …" (my emphasis). Ken, compadre, I admire the colloquial style. But let's not get carried away.

The preceding quote answers the question, were dinosaurs hung like … like … well, we mammals lack an adequate point of comparison. Anyway, they weren't. Fact is, we aren't certain the dinosaur had a penis at all, and if he did it was probably concealed. Dinosaur copulation was most likely accomplished by means of "kissing cloacae." The cloaca is the all-purpose body cavity that reptiles and birds use for copulation, urination, and defecation. You can see where this might reduce the romantic potential right off the bat. (Then again, maybe not.) One brings the cloacae of the partners into apposition; the penis or hemipenis, if any, extrudes from the male and is inserted into the female; and the generative material is translocated. Ken theorizes that dinosaur pudenda were similar to those of modern crocodiles, so we'll assume the males had penises, like crocs.

Sounds simple in principle, but given mass times acceleration, etc., one suspects that the potential for disaster rivaled Soyuz docking with Mir. For starters, as you point out, there's the issue of tails. Some have proposed a "lizard model" for dino sex: the male approached from the rear and twisted his tail underneath the female until their cloacae met. Ken reproduces a drawing along these lines by Beverly Halstead showing two mating diplodoci with tails charmingly entwined. But he considers this scenario anatomically unlikely — the typical dinosaur tail was held rigid for balance and could not easily twist.

Instead, Ken proposes what we might call housecat-style sex. The female squatted on her forelegs, raising her rear end and pushing her tail to one side, exposing her cloaca. The male mounted from behind and to the other side, supporting himself with his front legs on her back, possibly with one rear leg held off the ground to permit a closer conjunction of the organs.

I guess it would work, although having studied the illustrations of hypothetical dinosaur couplings I still think you'd want one of those taxiway guys at the airport with flashlights. Ken concedes as much. "How Stegosaurus, with the big plates on his back, managed to have sex is really not that difficult," he writes. "Again, with the female squatting in the front while standing on her hind legs, the male could easily rest his forelimbs on one side of her broad pelvis. More difficult to imagine is how the 150' long, 100+ ton Diplodocus-like sauropod Amphicoelias mated. Perhaps when the animals grew to that size, they had already passed their reproductive years." C'mon, Ken, have the courage of your convictions. Every day at the mall we see humans of dinolike proportions. Yet somehow they reproduce. Where there's a will there's a way.

By far the most riveting aspect of the book is artist Luis Rey's color rendering entitled (you knew this was coming) "Carnotaurus sex!" Had this been formatted as a Playboy-style centerfold, book sales would surely have shot through the roof. The dramatic head-on view depicts a pair of Tyrannosaurus-like critters in a posture that will remind some of a quarterback taking the snap. The male's expression of bug-eyed ecstasy indicates he has just delivered the goods, while the female's slightly nettled look suggests he was a couple minutes early, the pig. Nonetheless, the pterodactyls flying in formation overhead, the steamy geothermal glow, and the overall impression of tectonic forces in collision suggest that when dinosaurs had sex, the earth moved no matter what.